Automatic test equipment (ATE) refers to an automated, usually computer-driven, approach to testing devices, such as semiconductors, electronic circuits, and printed circuit board assemblies. A parametric measurement unit (PMU) is typically part of an ATE. A PMU is used during device testing to measure parameters, such as voltage and current, at a device pin, and to regulate those parameters. The PMU attempts to ensure that, during testing, proper parameter values are applied to the device under test (DUT).
A PMU typically includes circuitry for forcing a voltage and/or current to the DUT. Impedance (e.g., resistance) in a circuit path leading from this circuitry to the DUT can result in a voltage drop. This voltage drop reduces the amount of voltage that is applied to the DUT. Heretofore, PMUs were relatively low-current devices, e.g., on the order of 2 mA or less, making the voltage drop in the circuit path leading to the DUT relatively insignificant. However, with the advent of higher-current PMUs, e.g., on the order of 50 mA, the voltage drop on the circuit path to the DUT has become fairly significant. When the voltage drop is sufficiently high, as is often the case for higher-current PMUs, it can prevent the DUT from performing properly during testing, leading to inaccurate test results.